Television broadcasts, consumer video tape, different stored multimedia video formats, and live or taped over-the-air broadcasts are becoming increasingly more complex, having numerous channel formats, and increased requirements for adding new services and data associated with these systems. Different methods of transmission have been used for inserting content data containing additional information into the video signals of various broadcasting formats, including National Television System Committee (NTSC), Digital Advanced Television Systems Committee (ATSC), Sequentiel Couleur a Memoire (SECAM), or Phase Alternation Line (PAL) compliant broadcasting formats. Both the active and blank portions have been used. Different modifications to the luminance and chrominance carriers have been commonly exploited, such as teletex, where textual information is substituted for the video portion of the signal in the active portion of the video signal.
Other known data insertion techniques include the insertion of data into the vertical and horizontal blanking intervals of a video signal. A well known example is a closed captioning system used primarily as an aid to the hearing impaired community. With this type of data insertion technique, textual data is encoded into the vertical blanking intervals.
These prior art techniques have been fully exploited by different vendors, and thus, an additional method of transporting any content data is required. One technique, as disclosed in U.S. Pat. Nos. 5,663,766 and 5,929,920 to Sizer, II, assigned to Lucent Technologies Inc., adds a carrier signal that has been modulated by digital information into a video signal. This modulated carrier signal is at other than a frequency corresponding to a peak in the video spectrum. A receiver is arranged to sense optically the video signal and recover any encoded digital content data. Thus, the receiver optically views a screen luminance. This is not desirable for some applications because a receiver/decoder in that application must optically view screen luminance to recover the encoded digital content data.